Pebble heating and reaction chamber



April 21, 1953 I R. R. GOINS 2,635,864

PEBBLE HEATING AND REACTION CHAMBER Filed Dec, 28, 1948 2 SHEETS-SHEET 15 i I9 l9 I 1 i Q 1 29 U o l 5 23 INVENTOR.

R.R.GO|N5 WMW FIG 2 FIG ATTORNEYS Patented Apr. 21, 1953 PEBBLE HEATINGAND REACTION CHAMBER Robert R. Goins, Bartlesville, kla., assignor toPhillips Petroleum co Delaware mpany, a corporation of ApplicationDecember 28, 1948, Serial No. 67,678

1 Claim.

This invention relates to pebble heat exchangers. In one of its morespecific aspects it relates to pebble heat exchangers with heat exchangechambers having a high ratio of height to thickness. In another of itsmore specific aspects it relates to a method. of obtaining improved heatexchange between large volumes of fluent solid heat exchange materialand gaseous heat exchange material.

Processes which are carried out in so-called pebble heat exchangeapparatus utilize a flowing mass of solid heat exchange material, whichmaterial is heated or cooled to a desired temperature by passing a firstheat exchange fluid therethrough in a first direct heat exchange stepand is then caused to contact a second heat exchange fluid in a seconddirect heat exchange step so as to heat or cool the second heat exchangefluid. Conventional pebble heat. exchange apparatus generally comprisestwo chambers which may be disposed in substantially vertical alignment.The solid heat exchange material is introduced into the upper portion ofthe first chamber. That solid material forms a fluent bed which flowsdownwardly through the chamber in direct heat exchange with the firstfluid heat exchange material. The solid heat exchange material is heatedor cooled to a desired temperature in the heat exchange and is thenpassed to the lower chamber in which the solid heat exchange material iscaused to contact the second fluid heat exchange material in a seconddirect heat exchange relation.

Conventional pebble heat exchange chambers of pebble heat exchangers aregenerally formed as cylinders in which solid heat exchange material iscollected-in the form of a moving or fluent bed. Gaseous heat exchangematerial is introduced into the lower end of the cylindrical heatexchange material bed formed within the heat exchange chamber and at itsperiphery. The solid heat exchange material is usually drawn from a substantially central point in the bottom of the solid heat exchangematerial bed and is passed downwardly into a second heat exchangechamber where a second moving bed of solid heat exchange material isformed. One disadvantage of conventional pebble heat exchange chambersis that it is most diflicult to establish uniform how of solid heatexchange material within the chambers so as to supply uniformlyheated orcooled solid heat exchange material from one heat exchange chamber tothe other. In the withdrawal of solid heat exchange material from asubstantially central point in the bottom of such conventional heatgenerally called pebbles. used hereindenotes any solid refractorymaterial exchange chambers, the moving portion of the solid heatexchange material tends to describe a cone in the lower portion of thechamber. That material which is below and outside of the cone formed bythe moving solid heat exchange material remains in what is substantiallya stagnant area within the heat exchange chamber. At the same time, whensolid heat exchange material is introduced centrally into the upperportion of the heat exchange chamber, the top of the solid heat exchangematerial bed is formed as an inverted cone extending downwardly andoutwardly from the solid material inlet in the top of the chamber. Itwill thus be seen that that portion of the solid heat exchange materialwhich gravitates through the heat exchange chamber is bounded by acylinto its axis, the gas tends to channel through that portion ofmaterial making up the peripheral portion of the solid heat exchangematerial bed; The stagnant solid heat exchangematerial which comes torest in the stagnant areas formed below the bottom cone of the movingsolid heat exchange material bed, having once acted in heat exchangerelationwith the gaseous heat exchange material, acquires and remainsatapproximately the temperature of the incoming gas, thus failing tosubstantially enter into further heat exchange relation with the gaseousheat exchange material.

It remains, then, that only the moving portion of the solid heatexchange material will continue to enter into heat exchange with thegas. It will thus be seen that the gaseous heat exchange materialsflowing through the peripheral portion of the bed pass through arelatively thin layer of the solid material bed which will enter into aheat exchange relation therewith. For the reasons above described,relatively inefficient heat exchange is obtained in the operation ofsuch an apparatus when compared to the operation of the apparatus ofthis invention.

Solid heat exchange materialwhich is conventionally used in such heatexchange systems is of flowable' size and form whichlis capable ofcarrying relatively large amounts of heat from one heat exchange chamberto another and which has. sufiicient strength to withstand the mechan-Theterm pebbles as ical pressure and thermal changes within the heatexchange chambers without rapid deterioration or substantial breaking.Pebbles which are conventionally used in pebble heat exchangers aresubstantially spherical in shape and range from about oneseighl h inchtoabout onel inchintd ameter. In a processes utilizing extremely; highor extremely low temperatures, pebbles having a diameter of betweenabout one-fourth inch and; three-eighths inch are preferred Ijhe pebblesare formed of a refractory material=which-willi withstand temperaturesat least as high or as low as the highest or lowest temperature respec ttively, attained in the pebble; heat; exchange: chambers. The pebblesmost capable of withstanding temperature changes, within, pebble heaterapparatus include such refractory materials as metal alloys, ceramics,or other such mas" terials. Among specific materials which may be usedfor hie-h mp a u e: era ion; are-1 11mm carbi er;- um na; priclasaser-villa s c litez an a. ndemul-l a th r: singl rr admi tur wita hr tber,- --wi hiot cnmate iale Pebbl s f 'med: uch alsr hen nmperly;fired): rvesv ry: W l n temp ratur s; ometw thv standin mperatures: p;-ofi a ut .90?- b s wh ch: are= 1sed-max ev her, n r mr ta y ic: epend? pn-1 he, sele ed process Materials;whichmaybcmseds nlow tempera ure- Q pres e inc ud alumina;- alpmin mltatedupon reference =tothe= diagrammaticdrawh ingsin-iwhiclrliigure-ltis 'a side elevation-of azpebs. bleheatexchanger ofithisginvention. c Figure :2 is 69 a verticalsection-takenalong:line. za-z -vofihiguret 1- Fi ura -3 is: a: vertical;section; or: a: modified:.:. pebbletheat exchange chamber; Eigure '4 isa side elevation; partiallyiin section, ofia pebble; heatsex-l.changerl'showing-a; preferred:modificationofiithis invention; Figure; 5iis, a; vertical sectionltaken. along line 5-5 of Figured; In; Figure 1:the drawing, pebbleheat-1 ex.- changer. H1: comprises anupper heatexchange chamber; 12 andxazlower heattexchangeachamber: |3 ';whichcommunicate at thein l'ower-andsuppen ends; respectively; by! means. orthroat 14 Upper pebble collector chamber. I5? is; provided'cabovepebbleheat exchangechamber I2;ancl-com-muni-- cates: with the 'uppen portionof: chamber I 2 by 7a means of communicating throat i6. Pebble collectorchamber I5 is provided in its upper portion with at least one pebbleinlet conduit IT. The number of pebble inlet conduits provided in theupper portion of pebble collector chamber [5 will begdepfindfint uponthe depth cflchambertl'a. If a chamber of sufifrcient depthisa-utilizedg a single pebble inlet may be provided. The breadth ofchamber l5, when a single pebble inlet is utilized, must be such thatpebbles entering that inlet andvseekingl thetangle of repose will spreadout to-each Wall of the chamber. The angle of repose -vis tha apex angleof a stationary bed of RbblGS:WhiG at 'ng been dropped from a centralpoint and rrraintained as a stationary bed, have arrived at a staticposition. As the depth of the pebble-cellecto'rchamber is decreased,however;,; the number of pebble inlet conduits I! must be increased soas to allow sufiicient disposition of pebbl frem walllt ta lil n,v chmber. 1. ower pebble. le tor har ib rr v elow amb r aniac .m "ca rth heow pcrt o ic hcem cr; by ear soi' mlnunie tr of? hamber i2 and fiu di eex han e ma r inlets conduits zqar n v dc fln he w po tion ofchamber i3;Atleast' o n e pebble outlet" conduit 23 is provided in thelovverportion of pebble o l ctorl hamber i 8: f;'neb 01 ector mb r. l Tf. sufficient" ep h. e. pe ble outlet therefrom may be utilized; It will7 ordi narily be, desirable however, tofluti'lize the same;

mb o 'p bbl utl ts rom amb r 8'-= he.

umber i p bble. nlet n hamber I5 Suchns ruct on; would: insure unifo m.neb l rfiow. oug he p ratus: E1uhine as. n 9 itt i i n id r in eun r prt n iii-cham- Iber ndi filn nti whet n uiti fi is pr ided;

. throats may be form d lur lit of ots extending in a line; between thetwo end walls and; are preferably positioned equi-distant'the sidewalls-pfthechambers between which they com:

municate;

Referring to thedevice shown in; Figure 2'of' the drawing; bafilemember3 I is centrally provided-in-chan1ber i2 -so as to form uniform pebblepathsbetween the sidewalls of chamber 12 and the-sidewalls-of bafile 3i.In one modification of theinvention, bafile 3| may be perforate initslower end-andflu'idheat-exchangematerial inlets 2 l may-extend intobaffle ii. In such a modification; fluid heat-exchange material is-fed;into the interior of bailie-3-l and baill'efi'lacts as a distributionchamber'for-the fluid-heat exchange-material. Baffle 31 preferablyextendsfrom one end wall of chamber l-2 to its other end-1 wall; Theupper andllower ends of the bafile are preferably shaped so' that thesurfacesofthe bafileareparallel' to adjacentinterior surfaces of chambenI25; Interior: walls 32=-are previded-in= the upperportion of chamber I2and form eiiluent outlet chambers within the upper portion of chamberI2. Ef-- fluent outlet conduits 33 communicate between the heat exchangechamber within chamber I2 and the eilluent outlet chambers formed withinthe upper portion of chamber !2. Conduits 33 preferably are formed so asto receive an aspirating effect when flushing gas is passed through theeliluent outlet chambers. Conduits 33 preferably extend through walls 32at an angle and toward effluent outlet conduit 25. Walls 34 in the upperportion of heat exchange chamber I3 form effluent outlet chambers in theupperportion of that chamber. Ellluent outlet conduits 35 providecommunication between the heat exchange chamber within chamber I3 andthe effluent outlet chambers within the upper portion of chamber I3.Conduits 35 are preferably positioned similarly to conduits 33. Bafflemember 36 is provided in the lower portion of heat exchange chamber I3and preferably overlaps the vertical plane in Which the walls of throatiii are maintained. Fluid heat exchange material inlet conduits 22 maycommunicate with the lower portion of battle member 36. Bafile member 36thus forms a fluid heat exchange material distributing zone in its lowerportion. Pebble collector chamber I3 may be provided with walls 3? inits upper portion, which walls 31 form preheat exchange zones in theupper portion of chamber I8. Pebble inlet conduit [1 in the upperportion of chamber 15 and pebble outlet conduits 23 in the lower portionof chamber l8 communicate by means of elevator 38. The sloping floors ofchambers I 2 and I3 form pebble support means in each of those chambers.

'In the operation of the device shown in Figures land 2 of the drawing,pebbles are passed into the upper portion of chamber I5 and aredistributed therein so as to form a long narrow pebble bed. The pebblesmove downwardly through throat I6 as a flowing contiguous mass and intothe upper portion of pebble heat exchange chamber I2. The bed of pebblesis divided by baille member 3I within chamber I2 and the wide, thincontiguous stream of pebbles on each side of baffle member 3| passesdownwardly through chamber I2 to be joined together once again in thelower portion of chamber I2. Fluid heat exchange material is injectedthrough fluid heat exchange material inlet conduits 2| into the interiorof bafile member 3| in which the fluid heat exchange material isdistributed and from the lower portion of which the fluid heat exchangematerial is injected into the downwardly flowing streams of pebbles oneach side of bafille member 3!. Because of the constriction formed bythroat I4, the fluid heat exchange material cooled in the first heatexchange chamber are passed downwardly through throat I4 as a contiguousmass and are passed into the upper portion of heat exchange chamber l3.The pebbles form a fluent pebble bed within chamber I3 and flowdownwardly therethrough and out of chamber I3 through throat I9. Thepebble beds formed within chambers I2 and I3 are wide and thin ascompared to pebble beds in conventional pebble heat exchange chambers.Baffle member 35 retards the flow of pebbles through the central portionof pebble heat exchange chamber I3 and operates to aid in maintaininguniform peb ble flow through chamber I3. change material is injectedthrough fluid. heat exchange material inlet conduits 22 and is passedinwardly to a point adjacent the lower surface of baflle member 36. Thefluid heat exchange material is distributed under baflle 36 and passesoutwardly and upwardly through the pebble bed within chamber 13.Eflluent materials are removed from chamber I3 through eiiluent outletconduits 35 and pass into effluent outlet chambers within the upperportion of chamber I3 from which they are removed through eiiluentoutlet conduits 2'I. Removal of effluent material from chamber I3 may befacilitated by passing an inert flushing gas, such as steam, through theefiluent outlet chambers by means of inlet conduits 26 and efiluentoutlet conduits 2I. Pebbles from chamber l3 which pass downwardlythrough throat I9 are collected in chamber I8 and are distributed to thepebble outlet conduits 23 through which they are removed and are passedto elevator 38 which elevates the pebbles to pebble inlet conduits II.Gaseous materials may be pre-heated in the upper portion of chamber I8by passing the materials into the chambers formed between walls 3'! andthe outer walls of chamber 16. Such gases are injected thereinto throughinlet conduit 23 and are removed through outlet conduit 29. Preheatsections may be formed in chamber I8 by the pebbles without the aid ofwalls 31.

The lower portions of the chambers are shown in the device of Figure 2of the drawing as sloping downwardly and inwardly toward the pebbleoutlet of each chamber. It is preferred that the angle formed by thesloping sides of the chamber bottoms form an angle of between 60 and Byforming the chamber bottom in such a manner,stagnant areas aresubstantially removed from the chamber, thereby maintaining only movingpebbles within each of the chambers, without unduly restricting thechamber capacities for a given height. Baflle members 3| and 36 may beremoved from chambers I2 and I3,

respectively, when the width of the chambers is pebble bed will have noeffect upon the heat exchange or the pebble flow. Large volumes ofpebbles may thus be utilized in such an apparatus without affecting thepebble or gas flow therein. By maintaining the high ratio of height towidth of the pebble bed, uniformity of pebble flow is substantiallyincreased over that obtained in conventional pebble heaters. This isespecially true when the communicating throats comprise continuous slotsextending from one end wall of the heat exchange chamber to the other.In the modifications in which bailles 3i and 36 are ,removed fromchambers l2 and I3, respectively, the fluid heat exchange material maybe injected directly into the beds of flowing pebbles.

temperatures, fluid may be introduced into the Fluid heat ex- If a j isdesired to heat the pebbles to relatively high with either chamber 46 orchamber 47. Any of the bafiies disclosed in Figures 2, 4 and 5 may beutilized in any one of the chambers disclosed herein. The chambersdisclosed herein may also be employed in any combination, so that anychamber disclosed may be substituted for any other, or pairs may beemployed in inverted relationship to each other.

It is ordinarily desirable to seal one pebble heat exchange chamber fromthe other. A partial seal is accomplished by the pebble mass within theconstricted pebble throats. In order to increase the sealing effecttherein it is desirable to inject an inert gas, such as steam, into thethroats immediately above and below one of the heat exchange chambers.Best results are ordinarily obtained if the lower heat exchange chamberis sealed off by the injection of steam into its communicating throats.

Various other modifications will be obvious to those skilled in the artupon study of the above disclosure. Such obvious modifications arebelieved to be within the spirit and the scope of such disclosure.

I claim:

A pebble heat exchanger comprising in combination an upright, laterallyelongated, closed outer shell having two pairs of parallel sides; aclosure member extending laterally between each of the walls of saidshell so as to divide the cham-- ber formed within said shell into anupper section and a lower section; a perforate refractory arch extendinglaterally between each of the walls in the lower portion of the upperchamber section, forming a gas distribution zone between said arch andsaid closure member and a pebble heat exchange zone above said arch;pebble conduit means disposed along the length of said chamber, spacedequidistant from the side walls thereof, and extending through saidperforate arch and said closure member to said lower chamber section; aninlet conduit extending through said shell into said gas distributionzone; pebble inlet conduit means in the upper end of said shell; gaseouseflluent conduit means only in the upper end of said 10 upper chambersection; a first header mem ber positioned along one elongated side ofsaid shell; a second header member positioned along the opposite side ofsaid shell; first gaseous eifluent conduit means in said shell extendingonly from one side of the upper portion of said lower chamber section tosaid first header member; second gaseous effluent conduit means in saidshell extending from the opposite side of the upper portion of saidlower chamber section to said second header member; pebble outletconduit means in the lower end of said shell, equidistant the side wallsof said shell; fluid inlet means extending through said shell into thelower portion of said lower chamber section; and elevator meansextending from said pebble outlet conduit means in the lower end of saidshell to said pebble inlet conduit in the upper end oi said shell.

ROBERT R. GOINS.

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